Nutrition Chapter 11: Nutrients Involved in Bone Health

Biology of Bone

• 65% minerals-hardness

• 35% organic molecules- strength, durability, flexibility

Cortical/Compact bone characteristics

• 80% of our skeleton

• outer surface of all bones

• entire surface of small bones

Trabecular bone characteristics

• 20% of skeleton

• “spongy” bone

• protect bone from stress

• networks and columns of cavities

• fast rate of turnover based on hormones and nutrients

Where can you find trabecular bone?

• end of long bones like femur

• vertebral bones of spine

• sternum

• ribs

• skull

• pelvis

When does bone development end for males and females?

• males- 21 years old

• females- 18 years old

bone growth determines ____

bones growth determines size

bone modeling determines ______

bone modeling determines bone shape

Bone remodeling (in adulthood)

• replace old bone with new bone

• involves bone resorption

Resorption

breakdown of old bone

steps of resorption

1. osteoclast erodes bone surface using enzymes and acids, bone matrix breaks down

2. release calcium from bone → release into blood

formation

osteoblast synthesizes new bone matrix

collagen in matrix

hydroxyapatite- will crystallize to form bone

peak bone density for females and males

males-mid 20s

females- early 20s

Age of plateau and drop off of bone density

Plateau: 30s-40s

Drop off: 40+

Factors that impact low bone density

• late pubertal age

• inadequate Calcium intake

• low body weight

• physical inactivity during puberty

What do you use to find low bone density?

Dual energy X-ray absorptiometry (DXA or DEXA)

T score of DXA or DEXA

+1 to -1 normal

-1 to -2.5

less than -2.5 osteoporosis

Calcium functions in bone health

• provide structure for bones and teeth (99%)-along with collagen & hydroxyapatite crystals → maintain blood calcium

• assist with acid-base balance with blood

• assist in transmission of nerve impulses

• assist in muscle contraction (troponin and tropomyosin)

• maintain healthy blood pressure

• initiates blood clotting

• regulates hormones and enzymes

What happens when you have low blood calcium?

parathyroid gland secrete parathyroid hormone (PTH)

PTH will stimulate activation of vit D

What happens when PTH and Vitamin D work together?

• increased reabsorption of calcium by kidneys

• increased breakdown of bone to release calcium → stimulating osteoclast

• increase absorption of calcium by small intestine

What happens when you have high blood calcium?

inhibition of parathyroid secretion

suppression of vitamin D synthesis leads to ____

• decreased reabsorption of calcium by kidneys

• decreased breakdown of bone to release calcium

• decreased absorption of calcium by small intestine

Availability of dietary calcium

• absorption in duodenum

• active transport - Vitamin D

• passive transport/diffusion

what is bioavailability? and percentages with age

amount that body can absorb

based on age

infant-adolescent: 60%

older adults: 25%

Excess of Calcium

• excreted in feces

• but can interfere with absorption of other minerals

• Hypercalcemia: high blood calcium levels

  • usually people that have cancer or have high PTH

• symptoms: constipated, fatigue, confusion

Extreme excess of calcium can lead to ______

Extreme excess of calcium can lead to liver and kidney failure.

Deficiency of Calcium

Hypocalcemia: caused by kidney disease or someone that is vitamin D deficient, or low PTH

symptoms: muscle spasms, convulsions

extreme leads to osteoporosis

Vitamin D characteristics

• nutrient

• hormone

• works with PTH to regulate blood calcium

Functions of Vitamin D

• regulate transport of Calcium

• regulate transport of phosphorus

• signal kidney to either store or excrete calcium

• stimulate osteoclasts

• prevent some amount of malignant cancer growth

• involved in cell differentiation

What happens when Vitamin D + Calcium + Phosphorus?

crystallization → bone calcification

7-dehydrocholesterol (in skin) → UV light from sun →_______ → conversion occurs in liver → ______ → conversion occurs in kidneys → ________

7-dehydrocholesterol (in skin) → UV light from sun → cholecalciferol → conversion occurs in liver → calcidiol→ conversion occurs in kidneys → calcitriol (active form of vitamin D)

Excess of Vitamin D

• hypercalcemia

• over supplementation

Deficiency of Vitamin D

hypocalcemia

rickets: lack of mineralization in skeleton, in kids (sometimes have bowed legs)

osteomalacia: weak bones, loss of bone mass, in adults

Vitamin K characteristics

• fat-soluble

• stored in liver

• Phylloquinone-plants

• Menaquinone-produced by bacteria in large intestine, animals

Function of Vitamin K

• coenzyme for blood coagulation-prothrombin & procoagulants

• bone metabolism

  • help synthesize 2 proteins

    • osteocalcin: secreted by osteoblast

    • Matrix Gla protein: blood vessel walls, soft tissue, cartilage, and bone matrix

Deficiency of Vitamin K

rare

lack of coagulation → increased bleeding

fat malabsorption

long time overuse of antibiotics - affect bacteria in gut

Phosphorus characteristics

• intracellular

• anion (-)

• stored in bone

Functions of Phosphorus

Calcium + Vitamin D + P - form hydroxyapatite

used in fluid balance

structure ATP, DNA, RNA

phospholipid bilayer membrane

Excess of phosphorus

if you take an antacid with phosphorus

symptoms: muscle spasms, convulsions

Magnesium characteristics

major mineral

active + passive transport

kidney → blood magnesium levels

Functions of Magnesium

• in bone structure regulating formation of bone by regulating calcium, vitamin D, and PTH

• support Vitamin D metabolism

• blood clotting

• muscle contraction

• required for ATP, DNA, and protein synthesis

• cofactor of some enzymes to make DNA

Excess of Magnesium

excess supplement- can help with constipation but with a lot of water

symptoms: nausea, diarrhea, cramping, dehydration

Deficiency of Magnesium

• Hypomagnesemia and hypocalcemia

• weaker bones, osteoporosis

Functions of Fluoride

• combines with calcium and phosphorus - fluor hydroxyapatite

  • to protect teeth from bacteria

• stimulate bone growth

Fluoride characteristics

trace mineral

stored in teeth in bones to maintain structure

Excess of Fluoride

• Fluorosis- increased amount of protein in teeth enamel

  • makes teeth more porous

    • can get stained

enamel can also break down if using too many teeth whitening chemicals

Deficiency in Fluoride

cavities

bacteria levels increase, teeth structure decreases

Osteo porosis is characterized by:

• low bone mass

• deterioration of bone tissue

• fragile bones leading to bone fracture risk

• bone compaction: decreased height

• shortening and hunching of spine: kyphosis (dowager’s hump)

What is the shortening anf hunching of spine, also known as dowager’s hump?

Kyphosis

Osteoporosis Type I (menopausal)

• more common in women after menopause

• decrease in trabecular bone

• wrist and vertebrae fractures

Osteoporosis Type II (senile)

• more common after age 70

• decrease in trabecular and cortical bone

• hip and spine fractures

Risk factors of osteoporosis include:

• Age: metabolism and processing of Vitamin D decreases with age

• Gender: in women, there’s a decrease in estrogen levels

  • decrease in bone mass as well

  • 80% of Americans that have osteoporosis are women

• Genetics: more likely to have if relatives have it

• Tobacco: affects hormone levels

• Alcohol: lead to fractures

• Caffeine

• Poor nutrition: not eating vitamins C, K, D, and Magnesium

• Physical inactivity: exercise prevents bone loss and increased bone mass

Why are the risk factors of alcohol and caffeine important in osteoporosis?

both diuretics → increases urine output → excrete calcium → calcium loss